diff --git a/m4/malloc.m4 b/m4/malloc.m4
new file mode 100644
index 0000000..cb5cff3
--- /dev/null
+++ b/m4/malloc.m4
@@ -0,0 +1,35 @@
+#serial 6
+
+dnl From Jim Meyering.
+dnl Determine whether malloc accepts 0 as its argument.
+dnl If it doesn't, arrange to use the replacement function.
+dnl
+
+AC_DEFUN([jm_FUNC_MALLOC],
+[
+ dnl xmalloc.c requires that this symbol be defined so it doesn't
+ dnl mistakenly use a broken malloc -- as it might if this test were omitted.
+ AC_DEFINE(HAVE_DONE_WORKING_MALLOC_CHECK, 1,
+           [Define if the malloc check has been performed. ])
+
+ AC_CACHE_CHECK([whether malloc(0) returns a non-NULL pointer],
+                jm_cv_func_working_malloc,
+  [AC_TRY_RUN([
+    char *malloc ();
+    int
+    main ()
+    {
+      exit (malloc (0) ? 0 : 1);
+    }
+	  ],
+	 jm_cv_func_working_malloc=yes,
+	 jm_cv_func_working_malloc=no,
+	 dnl When crosscompiling, assume malloc(0) returns NULL.
+	 jm_cv_func_working_malloc=no)
+  ])
+  if test $jm_cv_func_working_malloc = no; then
+    AC_LIBOBJ(malloc)
+    AC_DEFINE(malloc, rpl_malloc,
+      [Define to rpl_malloc if the replacement function should be used.])
+  fi
+])
diff --git a/m4/realloc.m4 b/m4/realloc.m4
new file mode 100644
index 0000000..7695e89
--- /dev/null
+++ b/m4/realloc.m4
@@ -0,0 +1,35 @@
+#serial 6
+
+dnl From Jim Meyering.
+dnl Determine whether realloc works when both arguments are 0.
+dnl If it doesn't, arrange to use the replacement function.
+dnl
+
+AC_DEFUN([jm_FUNC_REALLOC],
+[
+ dnl xmalloc.c requires that this symbol be defined so it doesn't
+ dnl mistakenly use a broken realloc -- as it might if this test were omitted.
+ AC_DEFINE(HAVE_DONE_WORKING_REALLOC_CHECK, 1,
+           [Define if the realloc check has been performed. ])
+
+ AC_CACHE_CHECK([whether realloc(0,0) returns a non-NULL pointer],
+                jm_cv_func_working_realloc,
+  [AC_TRY_RUN([
+    char *realloc ();
+    int
+    main ()
+    {
+      exit (realloc (0, 0) ? 0 : 1);
+    }
+	  ],
+	 jm_cv_func_working_realloc=yes,
+	 jm_cv_func_working_realloc=no,
+	 dnl When crosscompiling, assume realloc(0,0) returns NULL.
+	 jm_cv_func_working_realloc=no)
+  ])
+  if test $jm_cv_func_working_realloc = no; then
+    AC_LIBOBJ(realloc)
+    AC_DEFINE(realloc, rpl_realloc,
+      [Define to rpl_realloc if the replacement function should be used.])
+  fi
+])